1. Field of Invention
The invention relates to a method for laying electric cables from a first to a second offshore wind power plant.
2. Description of the Prior Art
Such a laying operation in particular causes problems if a wind power farm is set up with a plurality of individual plants, and optionally, also one or more collecting points for the electrical connection.
The laying of electric cables between several offshore wind power plants, which are more particularly set up in numerous adjoining installations if sufficient space is available, is complicated and costly.
For every comparatively short laying distance for a cable, the latter must be cut to length from a supply and connected at its two end points. The laying of cables between offshore plants at sea has hitherto taken place through the use of large cable laying ships, which are loaded with the necessary power lines and have to be maneuvered close to the comparatively sensitive towers of the wind power plants. Even if, in addition, smaller boats and divers are used, it is still necessary for the cable in a complicated and time-consuming manner to be threaded into the first tower, preferably in the vicinity of the ocean floor, followed by connection, laying to the next plant, the large ship having to be maneuvered, cut to length, and then using a diver, is introduced into the bottom of the second tower of a wind power plant.
As a result of the expensive ship operating times and the large number of personnel involved, such a complicated laying represents a very considerable cost factor, which comes close to the actual tower assembly costs.
The problem of the invention is to provide a method for laying cables which reduces effort and costs to a significant extent.
According to the invention this problem is solved by a method having the features of the main claim. The subclaims provide advantageous embodiments.
Advantageously, the cable to be laid is already installed in the tower or foundation part of each wind power plant to its erection, and this can take place on land in an assembly bay or the like, or can take place without difficulty together with the final assembly and prior to tower erection. Each plant then contains the necessary cable type and length required for connecting it to the next plant or a collecting point. If several connections are desired, this can be implemented without difficulty.
Transportation of the cable as an integral component of the tower then causes no problem, and it is available in the correct length at the correct location without there being any additional logistical costs.
Thus, on erecting any wind power plant, the cable is at the correct location and can, but need not be, electrically connected by one end, because if the cable end is in the vicinity of the electrical connection, this does not represent a significant problem. After transporting a tow line to the target wind power plant, a second free cable end can be simply drawn up to it without a boat being required, other than for bringing out the tow line.
In this way, the plants are electrically interconnected to a collecting point.
Advantageously, with a guide pulley provided at a bringing out opening, the cable can be drawn out without damage from the tower of the particular wind power plant without an operator having to be present at this location. Any twisting of the cable can be avoided in that it is correspondingly laid, or in that a drum is placed in a rotary manner in the wind power plant tower from which the cable can be unwound.
During the transfer of the cable to the target wind power plant, the cable end can be raised with a float so that frictional drag on the ocean floor and the risk of jamming or locking on any obstacles are avoided. It is also possible for there to be numerous floats on the cable, which raises the latter from the ocean bed. It is subsequently possible to cut off the lines, or the floats can be flooded to enable the cable to sink to the bed.